Hello,
I am synthesizing single-crystal ceramic oxides for battery applications. Currently, there are performance issues arising from the broad size distribution of crystals produced during synthesis. The specific synthesis I use allows for a well-ordered, desirable lattice structure, but results in crystals from 500 nm up to 10 microns in size. The particles are also somewhat "sticky" and tend to clump together. While washing, sonicating, and filtering helps break down agglomerations, I have been unsuccessful in separating the very small particles from the very large particles. Are there some recommended non-destuctive separations that can be performed non-specialized equipment? I have looked into density gradient centrifugation, sieving, etc. but am uncertain where to start.
Thank you for your help!
Hi Alex,
separating such small particles is a very difficult task. You can immediately forget about sieving, since there are no sieves with a mesh size of less than 10 microns (the smallest laboratory sieves have a mesh size of 10 microns, but on an industrial scale the minimum size is 20 microns). The only possible way to separate particles with a size less than 10 microns is sedimentation in a liquid. This method is based on the difference in the settling rate of particles of different sizes: larger particles settle faster than smaller ones. There are laboratory and industrial devices for the implementation of sedimentary separation of particles.
The simplest equipment for sedimentation separation/analysis is the Imhoff cone: https://www.fishersci.de/shop/products/imhoff-cone-3/p-8015053?change_lang=true
Yes, Dr. Verlotski is correct. One technique which we use in our lab to speed up sedimentation is density gradient centrifugation. This method employs two different density solvents and creating a gradient of them so that the density varies with depth in the centrifuge tube. Then, when placed in the centrifuge the particles will separate into groups of different sizes and can be extracted using a pipette. If you want to read more about this method, I suggest you look at the paper below.
Article Bright Silicon Nanocrystals from a Liquid Precursor: Quasi-D...
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